The maximum-valency connectivity conjecture for Hom complexes

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Let GG be a graph, let dd be its maximal valency, and let KnK_n be the unlooped complete graph on nn vertices. For an integer k≥−1k\geq -1, write Hom(G,Kn)\text{Hom}(G,K_n) for the Hom complex and say it is kk-connected in the usual topological sense. Maximum-valency connectivity conjecture. If the maximal valency of GG is dd, then for all integers k≥−1k\geq -1 and n≥d+k+2n\geq d+k+2, the complex

Hom(G,Kn)\text{Hom}(G,K_n)

is kk-connected. The preceding proposition establishes the case k=0k=0 under the weaker-looking threshold n≥d+2n\geq d+2. This conjecture proposes higher connectivity as the number of available colors increases; the supplied passage gives no resolution.

References

Primary source

Eric Babson and Dmitry N. Kozlov, “Complexes of graph homomorphisms”, arXiv:math/0310056 (2005).

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